Research

Evolution of fungi.

Pattern and Process of Fungal Evolution.

We study the pattern and process of fungal evolution. We started by studying the pattern of evolution in terms of species and populations and now have begun to study the process. Our long term goal is to make fungi the best models for evolutionary biology. We focus on the key evolutionary event that forms the tree of life: speciation. Recently we have documented species divergences, compared phylogenetic and biological methods of species recognition, addressed the timing of species divergence, and evaluated selection acting on potentially adaptive genes. Now, we are using genetics and genomics to find genes that maintain species and facilitate adaptation.

Figure 1. Bayesian phylogeny made from exon sequence from Neurospora crassa isolates showing two, genetically differentiated populations in what had been thought to be one population. Comparison of the genomes of the Louisiana and Caribbean (dotted line) populations revealed the "islands of differentiation" seen in Figure 2. (Ellison et al. 2011. PNAS 107:2831-2836).

Figure 2. Island of differentiation. (A. chromosome 3, B chromosome 7) uncovered by genome scans of Neurospora crassa individuals from the Louisiana (LA) and Caribbean (Carib) populations. Genes in these islands are candidates for those important to adaptation. The mean annual low temperature in Louisiana is 10 degrees C lower in than the Caribbean and,using growth as a measure of fitness, Louisiana individuals were more fit than Caribbean individuals at low temperature. A Louisiana strain with a gene deletion for PAC 10 (prefoldin) or for MRH4 (RNA helicase) also showed lower fitness than wild type at low temperature, leaving intact our hypothesis that genes in the islands are important for adaptation to growth at low temperature. (Ellison et al. 2011. PNAS 107:2831-2836).